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From: Benjamin Herrenschmidt <benh@kernel.crashing.org>
To: Clemens Koller <clemens.koller@anagramm.de>
Cc: linux-fbdev-devel@lists.sourceforge.net, adaplas@gmail.com,
	Krzysztof Helt <krzysztof.h1@poczta.fm>,
	linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org,
	Geert Uytterhoeven <geert@linux-m68k.org>,
	Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [Linux-fbdev-devel] [PATCH 1/2] fb: add support for foreign	endianness
Date: Tue, 19 Feb 2008 11:35:53 +1100	[thread overview]
Message-ID: <1203381353.6740.59.camel@pasglop> (raw)
In-Reply-To: <47BA162C.5000807@anagramm.de>


On Tue, 2008-02-19 at 00:35 +0100, Clemens Koller wrote:
> Valdis.Kletnieks@vt.edu schrieb:
> > On Mon, 18 Feb 2008 08:18:47 +0100, Krzysztof Helt said:
> >> I know two fb drivers which use endianess information (pm2fb and s3c2410fb).
> >> Both resolve endianess at driver level. Actually, both handle it by setting special
> >> bits so the graphics chip itself reorder bytes to transform foreign endianess. 
> >> I understand that this patch is for chips which cannot reorder bytes by themselves.
> > 
> > Does anybody know of such a chip that's actually available in the wild?  Or are
> > we writing drivers for speculative possible chips?
> > 
> 
> I had troubles with the Silicon Motion SM501/SM502 endianess on PowerPC PCI vs. LocalBus.
> The chip also has a register to swap endianess, but that seems to only affect some
> LocalBus modes.
> The current fb and X drivers are working, but when it comes to font
> aliasing and hw-acceleration, the problems start to rise again...

Most "sane" gfx chips nowadays provide configurable surfaces that allow
to perform the swap when writing/reading from regions of the
framebuffer, with the ability to set a different swapper setting (based
on bit depth) per region.

Then there is also the risk that your PCI<->Localbus has been wired
improperly :-)

Ben.



  reply	other threads:[~2008-02-19  0:37 UTC|newest]

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-05 15:44 Anton Vorontsov
2008-02-05 19:07 ` Anton Vorontsov
2008-02-15  6:49 ` Andrew Morton
2008-02-15 16:45   ` Anton Vorontsov
2008-02-17  9:44     ` [Linux-fbdev-devel] " Geert Uytterhoeven
2008-02-18  7:18       ` Krzysztof Helt
2008-02-18 17:30         ` Valdis.Kletnieks
2008-02-18 17:37           ` Anton Vorontsov
2008-02-18 23:35           ` Clemens Koller
2008-02-19  0:35             ` Benjamin Herrenschmidt [this message]
2008-02-19 11:27               ` Clemens Koller
2008-02-19 12:05                 ` Andrew Morton
2008-02-19 12:22                   ` Clemens Koller
2008-02-20  0:47                   ` Valdis.Kletnieks
2008-02-20  0:50                     ` Benjamin Herrenschmidt
2008-02-20  0:56                   ` Paul Mackerras
2008-02-20 12:18                     ` Anton Vorontsov
2008-02-20 20:38                       ` Benjamin Herrenschmidt
2008-02-21  4:59                       ` Paul Mackerras
2008-02-20 15:43                     ` Clemens Koller
2008-02-16 11:49 ` Benjamin Herrenschmidt

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